Prime Plant Research Articles

Green leaf volatile production by plants: a meta‐analysis

666 I. Introduction 667 II. Biosynthesis 667 III. Meta-analysis 669 IV. The type of stress influences the total amount of GLVs released 669 V. Herbivores can modulate the wound-induced release of GLVs 669 VI. Fungal infection greatly induces GLV production 672 VII. Monocots and eudicots respond differentially to different types of stress 673 VIII. The type of stress does not influence the proportion of GLVs per chemical class 673 IX. The type of stress does influence the isomeric ratio within each chemical class 674 X. GLVs: from signal perception to signal transduction 676 XI. GLVs influence the C/N metabolism 677 XII. Interaction with plant hormones 678 XIII. General conclusions and unanswered questions 678 Acknowledgements 679 References 679 SUMMARY: Plants respond to stress by releasing biogenic volatile organic compounds (BVOCs). Green leaf volatiles (GLVs), which are abundantly produced across the plant kingdom, comprise an important group within the BVOCs. They can repel or attract herbivores and their natural enemies; and they can induce plant defences or prime plants for enhanced defence against herbivores and pathogens and can have direct toxic effects on bacteria and fungi. Unlike other volatiles, GLVs are released almost instantly upon mechanical damage and (a)biotic stress and could thus function as an immediate and informative signal for many organisms in the plant's environment. We used a meta-analysis approach in which data from the literature on GLV production during biotic stress responses were compiled and interpreted. We identified that different types of attackers and feeding styles add a degree of complexity to the amount of emitted GLVs, compared with wounding alone. This meta-analysis illustrates that there is less variation in the GLV profile than we presumed, that pathogens induce more GLVs than insects and wounding, and that there are clear differences in GLV emission between monocots and dicots. Besides the meta-analysis, this review provides an update on recent insights into the perception and signalling of GLVs in plants.

Phylogenetic, structural, and functional characterization of AMT3;1, an ammonium transporter induced by mycorrhization among model grasses.

In the arbuscular mycorrhizal (AM) symbiosis, plants satisfy part of their nitrogen (N) requirement through the AM pathway. In sorghum, the ammonium transporters (AMT) AMT3;1, and to a lesser extent AMT4, are induced in cells containing developing arbuscules. Here, we have characterized orthologs of AMT3;1 and AMT4 in four other grasses in addition to sorghum. AMT3;1 and AMT4 orthologous genes are induced in AM roots, suggesting that in the common ancestor of these five plant species, both AMT3;1 and AMT4 were already present and upregulated upon AM colonization. An artificial microRNA approach was successfully used to downregulate either AMT3;1 or AMT4 in rice. Mycorrhizal root colonization and hyphal length density of knockdown plants were not affected at that time, indicating that the manipulation did not modify the establishment of the AM symbiosis and the interaction between both partners. However, expression of the fungal phosphate transporter FmPT was significantly reduced in knockdown plants, indicating a reduction of the nutrient fluxes from the AM fungus to the plant. The AMT3;1 knockdown plants (but not the AMT4 knockdown plants) were significantly less stimulated in growth by AM fungal colonization, and uptake of both 15N and 33P from the AM fungal network was reduced. This confirms that N and phosphorus nutrition through the mycorrhizal pathway are closely linked. But most importantly, it indicates that AMT3;1 is the prime plant transporter involved in the mycorrhizal ammonium transfer and that its function during uptake of N cannot be performed by AMT4.

Cis-Jasmone primes defense pathways in tomato via emission of volatile organic compounds and regulation of genes with consequences for Spodoptera exigua oviposition

The role of cis-Jasmone (CJ) in priming plant defense against insect feeding is well documented in the literature. However, little is known about the role of CJ in mediating oviposition behavior of insects via changes in emission of volatile organic compounds (VOCs). Here, we hypothesized that foliar application of CJ will prime induction of plant defense in tomato via enhanced emission of VOCs with consequences for oviposition by Spodoptera exigua, an important pest of tomato. First, we quantified VOCs and the transcript levels of key genes that encode VOC biosynthesis in CJ-treated plants with S. exigua caterpillar infestation (CJI), untreated plants with S. exigua caterpillar infestation (UI), CJ-treated plants without S. exigua caterpillar infestation (CJ), and untreated plants without S. exigua caterpillar infestation (U). Next, oviposition preference of S. exigua was compared between CJI and UI, and between CJ and U. Gas chromatograph coupled-mass spectrometry (GC-MS) analyses showed that several key plant VOCs, including green leaf volatiles, monoterpenes, and a sesquiterpene, were emitted in significantly higher amounts in CJI compared to UI, CJ, or U. Consistent with the GC-MS results, the transcript levels of certain terpene synthase genes involved in the biosynthesis of many VOCs were higher in CJI plants. Consequently, S. exigua laid fewer numbers of eggs on CJI than UI. Moreover, in an in vitro oviposition choice test using filter paper, S. exigua laid significantly fewer eggs on filter papers containing VOCs from CJI compared to UI. These results indicate that CJ treatment followed by caterpillar infestation can prime tomato plant defense with potential ramifications for insect oviposition.

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Nowadays to lessen the influence of salinity on crop performances such as germination, seedling growth and yield, several actions are undertaken; for example the use of different priming methods, antioxidants and plant growth controllers. Seed priming, best fits in this study on maize crop and is controlled by hydration process followed by re-drying that allows pre-germination which enhanced metabolic activities to proceed rapidly. The objective of this study was to investigate how seed salt priming increases maize crop performance thereby enhancing yields by stimulating the plant physiological processes. Here, sodium chloride and calcium chloride primed seeds germinated earlier than unprimed one. Primed maize seeds had better efficiency for water absorption. Likewise, energetic metabolic activities in germination process commence much earlier than radicle and plumule appearance. Priming of seeds with salt solution enables them to break their dormancy and escape from disease causing agents and competent seeds of weeds. Seed priming with NaCl and CaCl2 had significant effects on germination, early growth, number branches, number of cobs and grain yield. This increase in growth traits likely helps to reduce the competition for water and nutrients with associated improvements in seed yield. Besides, it makes seed priming practice a viable option for the successful use of maize in irrigation areas. Sodium chloride (NaCl) priming increases shoot length while, calcium chloride (CaCl2) priming increases root length. Seeds grown in vertisol soil prefers seed priming for better stand establishment and crop yield whereas; seeds in lithosol soils prefer priming for better seed germination and increase number cob. Key words: Seed salt priming, maize, salt tolerance, germination rate, physiology.

Fructans As DAMPs or MAMPs: Evolutionary Prospects, Cross-Tolerance, and Multistress Resistance Potential.

This perspective paper proposes that endogenous apoplastic fructans in fructan accumulating plants, released after stress-mediated cellular leakage, or increased by exogenous application, can act as damage-associated molecular patterns (DAMPs), priming plant innate immunity through ancient receptors and defense pathways that most probably evolved to react on microbial fructans acting as microbe-associated molecular patterns (MAMPs). The proposed model is placed in an evolutionary perspective. How this type of DAMP signaling may contribute to cross-tolerance and multistress resistance effects in plants is discussed. Besides apoplastic ATP, NAD and fructans, apoplastic polyamines, secondary metabolites, and melatonin may be considered potential players in DAMP-mediated stress signaling. It is proposed that mixtures of DAMP priming formulations hold great promise as natural and sustainable alternatives for toxic agrochemicals.

Defense Priming and Jasmonates: A Role for Free Fatty Acids in Insect Elicitor-Induced Long Distance Signaling.

Green leaf volatiles (GLV) prime plants against insect herbivore attack resulting in stronger and faster signaling by jasmonic acid (JA). In maize this response is specifically linked to insect elicitor (IE)-induced signaling processes, which cause JA accumulation not only around the damage site, but also in distant tissues, presumably through the activation of electrical signals. Here, we present additional data further characterizing these distal signaling events in maize. Also, we describe how exposure to GLV increases free fatty acid (fFA) levels in maize seedlings, but also in other plants, and how increased fFA levels affect IE-induced JA accumulation. Increased fFA, in particular α-linolenic acid (LnA), caused a significant increase in JA accumulation after IE treatment, while JA induced by mechanical wounding (MW) alone was not affected. We also identified treatments that significantly decreased certain fFA level including simulated wind and rain. In such treated plants, IE-induced JA accumulation was significantly reduced when compared to un-moved control plants, while MW-induced JA accumulation was not significantly affected. Since only IE-induced JA accumulation was altered by changes in the fFA composition, we conclude that changing levels of fFA affect primarily IE-induced signaling processes rather than serving as a substrate for JA.

A push-button: Spodoptera exigua oviposition on Nicotiana attenuata dose-independently primes the feeding-induced plant defense

abstractInsect oviposition on a plant often precedes the attack by herbivorous larvae. We recently discovered that oviposition by Spodoptera exigua moths on the desert tobacco Nicotiana attenuata primes the induction of 2 defense traits, a phenylpropanoid and activity of protease inhibitors, in response to larval feeding. Oviposition-experienced plants suffer a reduced feeding damage by less and smaller larvae than unexperienced control plants. The increased resistance of oviposition-experienced plants requires the plant's ability to activate its biosynthesis of phenylpropanoids via a Myb transcription factor. Oviposition by S. exigua on N. attenuata is highly variable with respect to the amount, distribution and localization of the eggs on the plant. This raises the question, whether the plant's priming of herbivore defense depends on the egg number and localization. S. exigua moths prefer the oldest leaves for oviposition and yet prime defense-induction in the larval attacked young systemic leaves. Neither the levels of the primed defense traits, nor the affected larval mortality correlate with the number of eggs a plant previously received. This suggests that upon S. exigua oviposition, N. attenuata is shifted – independently of the egg-dose – into a primed state that is responding stronger to the feeding larvae than unprimed plants.

Control of Tomato yellow leaf curl virus disease by Enterobacter asburiaeBQ9 as a result of priming plant resistance in tomatoes

Enterobacter asburiae BQ9, a plant-growth-promoting rhizobacterium, was shown to promote tomato plant growth and induce resistance to Tomato yellow leaf curl virus (TYLCV) under greenhouse conditions. Compared with mock-treated tomato plants, plants that were pretreated with BQ9 had increased fresh mass and significantly reduced disease severity and 52% biocontrol efficacy was achieved 30 days after inoculation. The expression of defense-related genes PR1a and PR1b and the H 2 O 2 burst were quickly induced in BQ9 pretreated plants. Antioxidase activity analysis showed that the activities of phenylalanine ammonia lyase, peroxidase, catalase, and superoxide dismutase increased significantly in BQ9 pretreated plants. Our results suggest that the plant-growth-promoting rhizobacterium BQ9 induced a priming of the plant defense responses to TYLCV by increasing the expression of defense response genes, and the induced resistance was mechanistically connected to the expression of antioxidant enzymes and the production of H 2 O 2 .

Beta-aminobutyric acid priming of plant defense: the role of ABA and other hormones.

Plants are exposed to recurring biotic and abiotic stresses that can, in extreme situations, lead to substantial yield losses. With the changing environment, the stress pressure is likely to increase and sustainable measures to alleviate the effect on our crops are sought. Priming plants for better stress resistance is one of the sustainable possibilities to reach this goal. Here, we report on the effects of beta-aminobutyric acid, a priming agent with an exceptionally wide range of action and describe its way of preparing plants to defend themselves against various attacks, among others through the modulation of their hormonal defense signaling, and highlight the special role of abscisic acid in this process.

Ethylene: Traffic Controller on Hormonal Crossroads to Defense.

Ethylene (ET) is an important hormone in plant responses to microbial pathogens and herbivorous insects, and in the interaction of plants with beneficial microbes and insects. Early ET signaling events during these biotic interactions involve activities of mitogen-activated protein kinases and ETHYLENE RESPONSE FACTOR transcription factors. Rather than being the principal regulator, ET often modulates defense signaling pathways, including those regulated by jasmonic acid and salicylic acid. Hormonal signal integrations with ET steer the defense signaling network to activate specific defenses that can have direct effects on attackers, or systemically prime distant plant parts for enhanced defense against future attack. ET also regulates volatile signals that attract carnivorous enemies of herbivores or warn neighboring plants. Conversely, ET signaling can also be exploited by attackers to hijack the defense signaling network to suppress effective defenses. In this review, we summarize recent findings on the significant role of ET in the plants' battle against their enemies.

Editorial: Plant responses to bacterial quorum sensing molecules.

Editorial: Plant responses to bacterial quorum sensing molecules.

Seed priming stimulate germination and early seedling growth of Chinese cabbage under drought stress

Drought stress influence seed germination and seedling growth of many plants. Seed priming could be used to alleviate the depressive effects of drought stress. The improving effects are influenced by many factors including priming methods, plant species and drought intensity. The mechanisms of drought tolerance induced by seed priming have not been clearly elucidated. The study was carried out to assess whether drought tolerance could be enhanced by seed priming at the germination stage and characterize the potential physiological and biochemical alternation of drought tolerance in Chinese cabbage. The seeds were soaked at 20°C for 8h in distilled water, 200mmol/l potassium nitrate (KNO3), 200mmol/l urea, respectively. Both primed and unprimed seeds germinated under six levels of drought stress (0, −1.0, −2.0, −3.0, −4.0 and −5.0MPa osmotic potential) induced by PEG 6000. Results indicated that germination traits (germination percentage, potential and seedling vigor index) of Chinese cabbage all decreased gradually with increasing drought intensity. Three seed priming types including water, KNO3 and urea all increased germination traits at all levels of drought stress as compared to the unprimed seed. The enhanced drought tolerance conferred by seed priming treatments is associated with the modulating peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activities and levels of soluble sugar and proline. The results suggested that priming could serve as an appropriate treatment to increase the germination and early seedling growth of Chinese cabbage under drought stress conditions.

Indole is an essential herbivore-induced volatile priming signal in maize.

Herbivore-induced volatile organic compounds prime non-attacked plant tissues to respond more strongly to subsequent attacks. However, the key volatiles that trigger this primed state remain largely unidentified. In maize, the release of the aromatic compound indole is herbivore-specific and occurs earlier than other induced responses. We therefore hypothesized that indole may be involved in airborne priming. Using indole-deficient mutants and synthetic indole dispensers, we show that herbivore-induced indole enhances the induction of defensive volatiles in neighbouring maize plants in a species-specific manner. Furthermore, the release of indole is essential for priming of mono- and homoterpenes in systemic leaves of attacked plants. Indole exposure markedly increases the herbivore-induced production of the stress hormones jasmonate-isoleucine conjugate and abscisic acid, which represents a likely mechanism for indole-dependent priming. These results demonstrate that indole functions as a rapid and potent aerial priming agent that prepares systemic tissues and neighbouring plants for incoming attacks.

Priming crops against biotic and abiotic stresses: MSB as a tool for studying mechanisms.

Biotic and abiotic stresses are the main problems affecting agricultural losses. Consequently, understanding the mechanisms underlying plant resistance or tolerance helps us to develop fruitful new agricultural strategies. These will allow us to face the challenges of producing food for a growing human population in a sustainable and environmentally friendly way. To compensate for their sessile life and face a broad range of biotic and abiotic stresses, plants have evolved a wide range of survival and adaptation strategies. Amongst them, higher plants are capable of inducing some stress “memory,” or “stress imprinting.” Bruce et al. (2007) define stress imprinting as genetic or biochemical modifications induced by a first stress exposure that leads to enhanced resistance to a later stress. This phenomenon also known as “priming” results in a faster and stronger induction of basal resistance mechanisms upon subsequent pathogen attack, or greater tolerance against abiotic stresses (Pastor et al., 2013). Basal resistance by itself is too weak to protect against virulent pathogens, since it constitutes a residual level of resistance after immune suppression by the pathogen through co-evolution (Walters and Heil, 2007; Conrath, 2011). However, Ahmad et al. (2010) proposed that priming-inducing stimuli can provide more effective basal resistance, particularly when an earlier defense response precedes immune suppression by the invading pathogen. Following perception of microbe-associated molecular patterns (MAMPs), recognition of pathogen-derived effectors or colonization by beneficial microbes, priming can also be induced by treatment with some natural or synthetic compounds or even by wounding (Conrath, 2011). Through priming plants are able to induce responses to a range of biotic and abiotic stresses, providing low-cost protection in relatively high stress-pressure conditions. Despite priming phenomena having been widely described, the molecular mechanisms of defense priming are still unclear. Such techniques are now starting to emerge as a promising alternative for sustainable modern pest management in the field, since some pesticides have been shown to actually exert their known plant health- and yield-increasing effects through priming (Beckers and Conrath, 2007). From an ecological point of view, the benefits of priming are clear: rather than leading to the costly and potentially wasteful activation of defenses, a metabolic state of alert is induced after an initial infection, enabling a rapid intense resistance response to subsequent attacks. Thus, this strategy appears promising for crop protection purposes (Walters and Heil, 2007).

Cnicus benedictus as a potential low input oil crop

Cultivation of oil plants in locations less suited for prime oil plants may provide variation in vegetable oil availability and may contribute to land use diversification. Blessed thistle (Cnicus benedictus L.) offers potential as an alternative oil crop for cultivation in central Europe. Fruit yields of approximately 2.0–2.5 t/ha and oil yields of 500–700 kg/ha result from sowing in early autumn. Plants are cultivated on medium‐quality soil and demand only limited nitrogen fertilization. Linoleic acid dominates among the fatty acids of C. benedictus oil, similar to other Asteraceae fruit oils. The high tocopherol content in the oil is composed of over 90% α‐tocopherol. C. benedictus fruits contain the lignan glycoside arctiin with 2.5% of grain dry mass.Practical applications: Cnicus benedictus plants can be cultivated in middle Europe with low agricultural costs and efforts. Plants grow well on medium‐quality soil and are not susceptible to illnesses and pests. Regular fruit yields are approximately 2.0–2.5 t/ha. C. benedictus oil is a good source of linoleic acid (>70% of total fatty acids) and of α‐tocopherol (>90% α‐tocopherol of total tocopherols). The oil appears attractive for cosmetics and for technical applications, e.g., as a coating agent. C. benedictus oil may also be suitable for human nutrition, an admission as appropriate food ingredient provided. In addition, C. benedictus oil cake can be exploited as a source for the lignan glycoside arctiin.Fruits of Cnicus benedictus, Asteraceae, contain a fatty oil with high linoleic acid and α‐tocopherol contents. Grain yields of 2.0–2.5 t/ha on medium‐quality soil classify C. benedictus as promising alternative oil crop in mid‐Europe.

Ethnomedicinal knowledge of the most commonly used plants from Deosai Plateau, Western Himalayas, Gilgit Baltistan, Pakistan

Ethnopharmacological relevanceThe current survey was aimed to identify the prime important medicinal plants in terms of medicines and further pharmacological screening of such plants. As far as, we know, no reported data from Deosai Plateau have been published and this is the first documented information of the study area. Material and methodsEthnomedicinal information of plants was collected through semi-structured interviews through a participatory rural appraisal (PRA) method. Results and discussionThis study provided information of 50 medicinal plant species used to treat 29 different ailments. A total of 42 species (84%) were herbs while shrubs and subshrubs were represented by 8 species (16%). Leaves (37%) were the predominant plant parts followed by, roots (27%), aerial parts (13%), flowers (12%), fruit (7%), seeds (3%), and tuber (1%). Method of preparation fall into five categories including infusion (31%), paste (23%), decoction (20%), powder (18%), and juice (8%). ConclusionThe study area is rich in medicinal plant diversity growing in wild. Our efforts in this regard are only a little contribution to the ethnobotanical study of this area focusing on medicinal plants while more clinical studies are required in future to prove such claims of local inhabitants.

Complete genome sequence of a plant associated bacterium Bacillus amyloliquefaciens strain UCMB5033

Bacillus amyloliquefaciens UCMB5033 is of special interest for its ability to promote host plant growth through production of stimulating compounds and suppression of soil borne pathogens by synthesizing antibacterial and antifungal metabolites or priming plant defense as induced systemic resistance. The genome of Bacillus amyloliquefaciens UCMB5033 comprises a 4,071,167 bp long circular chromosome that consists of 3,912 protein-coding genes, 86 tRNA genes and 10 rRNA operons. doi:10.4056/sigs.4758653

Complete genome sequence of a plant associated bacterium Bacillus amyloliquefaciens subsp. plantarum UCMB5033.

Bacillus amyloliquefaciens subsp. plantarum UCMB5033 is of special interest for its ability to promote host plant growth through production of stimulating compounds and suppression of soil borne pathogens by synthesizing antibacterial and antifungal metabolites or priming plant defense as induced systemic resistance. The genome of B. amyloliquefaciens UCMB5033 comprises a 4,071,167 bp long circular chromosome that consists of 3,912 protein-coding genes, 86 tRNA genes and 10 rRNA operons.

Sensible Dress: the Sight, Sound, Smell and Touch of Late Ertebølle Mesolithic Cloth Types

The aim of this article is to investigate the sight, sound, smell and touch of different cloth types in the Late Ertebølle of southern Scandinavia and to argue that such an approach provides stimulating new insights into an area of material culture that has previously been studied by archaeologists in a highly empirical manner. The archaeological evidence drawn together in this article points to this as a time when furs and skin products were of prime importance and plant fibres were the basis for knotted nets, looped cloth and basketry. In the archaeological literature these cloth types are usually treated separately and described according to the species of raw materials, such as pine marten fur, or the technology of their production, such as couched button-hole stitch. Using an experiment where participants are asked to handle modern cloth types and answer structured questionnaires, it is possible to create a sensory description of these cloth types. These descriptive results are then used to reconsider aspects of cloth and clothing in the Late Ertebølle of southern Scandinavia. By moving from the standard technological description to a sensory description, the Mesolithic cloth types investigated in this article are placed within a sensory and phenomenological theoretical framework. The presentation of these results seeks to provide a new description of these materials and allow archaeologists to revaluate the culturally-embedded nature of cloth and clothing at that time.

Green Leaf Volatiles: A Plant’s Multifunctional Weapon against Herbivores and Pathogens

Plants cannot avoid being attacked by an almost infinite number of microorganisms and insects. Consequently, they arm themselves with molecular weapons against their attackers. Plant defense responses are the result of a complex signaling network, in which the hormones jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) are the usual suspects under the magnifying glass when researchers investigate host-pest interactions. However, Green Leaf Volatiles (GLVs), C6 molecules, which are very quickly produced and/or emitted upon herbivory or pathogen infection by almost every green plant, also play an important role in plant defenses. GLVs are semiochemicals used by insects to find their food or their conspecifics. They have also been reported to be fundamental in indirect defenses and to have a direct effect on pests, but these are not the only roles of GLVs. These volatiles, being probably one of the fastest weapons exploited, are also able to directly elicit or prime plant defense responses. Moreover, GLVs, via crosstalk with phytohormones, mostly JA, can influence the outcome of the plant’s defense response against pathogens. For all these reasons GLVs should be considered as co-protagonists in the play between plants and their attackers.